Internet multi-core computing is the latest development of the exchange. MPLS label switching to forward part and control part of the IP routing together to speed up the forwarding rate. Moreover, MPLS can run over any link layer technology, which simplifies to based on SONET / WDM and IP / WDM structure of the transformation of next generation optical Internet. Here, the major label forwarding describe the production process and how MPLS IP packet forwarding.
MPLS label stack header 32-bit MPLS header stack includes the following areas (Figure 1):
MPLS tag bearing the actual value of the tag region (20);
CoS region (3) for the packet through the network applied to the packet on the queue and discard scheme;
Stack region (S region, a), used to support the tag stack sequence;
TTL region (8), providing traditional IPTTL function.
Label forwarding production process 1. Router Between routing protocols or static routes through routing table generated.
Shown in Figure 2, assume that the way A, B, C, D four routers running OSPF protocol, A to D router, router to learn the route segment 211.91.168.0/24.
2. Routers running MPLS routing table for the routing label distribution.
Figure 3A, B, C, D four router’s routing table has 211.91.168.0/24 route segment, assuming that the routers are running MPLS protocol, each router will then assign a label for the route .
3. Via LDP / RSVP protocol found MPLS neighbors.
Assuming the router interface start LDP protocol. Through the LDP discovery protocol, A MPLS router to know its neighbor router B, B router that A, C its MPLS neighbors, C router that B, D to its MPLS neighbors, D of the MPLS neighbors to C.
4. Circular route label will be playing to its MPLS neighbors.
The router to play the label MPLS routing notifications to their neighbors, regardless of whether learning from its neighbor to the routing tag. This route 211.91.168.0/24 to each router in the label situation shown in Figure 4.
5. Its next hop router, the router will label the notice published in its turn. Often in practical applications will be the destination was not the local router IP packet forwarding to the next hop. Therefore, in MPLS, the routers only its next hop router, the label added to the notice published in its turn. 211.91.168.0/24 forward for the corresponding segment shown in Figure 5.
IP packet forwarding process in the MPLS network
1. MPLS router entry routing table according to the destination address lookup.
Figure 5 patients, assuming a destination address of IP packets arrive for the 211.91.168.0/24 router A. A router at this time will find its routing table, find the route next hop for the router B.
2. IP packet marked with the label, forward it to the next hop router.
The above example, Router A will be the destination address of IP packets to 211.91.168.0/24 to tag 20, forwarded to its next hop router B.
3. Find the next hop router, forwarding, replace tag, continue forward.
The above example, when playing a tag IP packets arrive at router B, router is no longer under the destination address to find routing table, but rather find the tag under the label forwarding. Outbound from A to B labels correspond to the inbound label, that is, notice to the A, B label. B routers tag replacement, will replace its inbound outbound tab labels, which replace the label with label 30, 20, and then forwarded to its next hop router C. C for label switching routers also will be IP packets with a tag of 40 to give D router.
4. Egress router to find its forwarding, the destination network is found, pop label, sent to the corresponding port deal.
The above example D forwarding router will find the label and found that the IP packet destined for itself, then the pop-up label. Label switching process is completed.
VPN in the MPLS Implementation RFC2547bis defined to allow service providers to use its IP backbone network to provide users with a mechanism for VPN services. RFC2547bis also known as BGP / MPLSVPN, because BGP is used to publish in the provider backbone VPN routing information, and MPLS VPN services are used to transmit from one VPN site to another site. First MPLSVPN common terms used in to make a note, and then explain the basic principles and MPLSVPN achieve common network.
MPLS / VPN terminology commonly used in
PE router: Also known as provider edge router. The router is responsible for client network access to provider networks.
P router: router, also known as provider. P routers are not connected to any network provider of CE device router.
CE router: also known as the user edge devices. CE routers connected to one or more Provider Edge (PE) router data link to provide users with access to the service provider.
VPN-IPV4 address: VPN users often use private addresses to plan their own network. When the different VPN users to use the same private address lookup route planning problem occurs.
Routing distinction breaks RD: Routing distinction breaks RD VPN-Ipv4 address that the first 8 bytes, is used to distinguish between different VPN in the same private network address.
Routing target RT: RT for the MP-BGP extended community attributes in one. Route target attribute defines the PE router, the routing of a release site (VRF) of the collection. PE router uses this attribute to the input remote route to the VRF for restraint.
VPN Routing Forwarding (VRF): Each PE router connected directly to its site to maintain a VRF. Links for each user is mapped to a specific VRF. PE router for each VRF and a port associated.
VPN in the MPLS network to achieve
Network topology description Suppose a service provider has an IP backbone network, for different companies to provide BGP / MPLSVPN services. Networks have three PE routers, connected to four different user sites.
Figure 6, CE1 and CE3 belong to the same VPN1, CE2 and CE4 belong to another VPN2. Site 1 (CE1) any of the hosts with site 3 (CE3) any of the host
Communicate . Site 2 (CE2) any of the hosts with site 4 (CE4) in any host.
Routing process of learning
In a user site can be forwarded to the remote site VPN service before will
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